Gyroscopic top



Patented a... M, 1922.

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EDME ETIEN'NE. JOSEPH BONNEAU, OF PARIS, FRANCE.

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Application filed January 1 5, 1919. Serial 271,280.

To all whom it may concern:

Be it known thatI, EDME ETIENNE J osErH BONNEAU, of Rue Beudant, Paris,France,

furnish a stable indication of the verticalor of the plane of thehorizon. 4 The proper characteristics ofthis im- 15 provement'proceedfrom the following considerations The various present gyroscopes of thetop kind, that is to say supported by a single .pivot, have for theirtype the gyroscopic sextantof Fleuriais who has defined the conditionsof construction and use thereof to be viz. 1. Placing the centre ofgravity a little below the point of the pivot. j 2. Employing as fine apivot point as the conditions of mechanical resistance permit. 3; Onlyutilizing the top at extremely high speeds (4,000 to 5,000 revolutions).

A gyroscope of this kind when a very low speed of rotation is impartedthereto preserves an easy pendular stability, but as soon as itsrotation becomes rapid its movement is solely governed by the.following, phenomena: If its axis be supposed to be inclined to thevertical, the effect of the weight is to cause said axis to. describewith a uniform speed a circular cone around the vertical (precession).'At the same time the asym- -40 metric friction of the point bearingobliquely upon its bearing develops at the point of contact a smallhorizontal frictional force which gives rise to a couple of 'gyros'taticreaction tending to correct the oblique axis of the gyroscope and tobring back the speed of recession.

he result of these two actions is definiti-vely to bring back'slowlythis axis into the vicinity of the vertical when it has beent0 shiftedaway therefrom, by a' series of circular oscillations smaller andsmaller and very long in vanishing, its pole describing in space aloxodromic trajectory.

Experience has shown that such apparatus are of little use in practiceas indicators of the vertical by reason in particular of the followingdisadvantages:

1. These instruments cannot furnish instantaneous indications, theslowness of the oscillations of the axis about its position ofequilibrium compelling this to be defined by means of maximumelongations of the axis observed on each side" of it.

2. By reason of the lowering of the centre of gravity below the point ofthe pivot, these 1nstruments are very sensitive to all the forces actinglaterally on the top for example to horizontal accelerations, which, if

they are important (as on board flying machines), completely falsify theobservations.

3. None of these disadvantages can be remedied (by augmentation of thependular stability or increase of the speed of rotation) withoutdeveloping the other disadvantage simultaneously.

It has only been possible hitherto to obtain imperfect instruments, bychoosing for them empirically mean conditions.

The invention forming the subject-mat-- ter of the present inventionrelates to an improvement in gyroscopic top for causing the axis of thistop to take, under the effect of the rotation alone of the latter,without the help of any auxiliary member, a polar setting in thedirection of the vertical, without conical precession and to remain instable equilibrium in this position.

This improvement is essentially characterized in that the top has aspherical pivot" the centre of which coincides with the centre ofgravity of this top and which rotates on a step bearing having a greaterradius of curvature than the radius of the sphere of this pivot, so thatthe latter is in contact at one point with the said bearing.

- By way of example, the invention is represented inthe accompanyingdrawing in which: I

Figure 1 shows in vertical section the present improved arrangement ofgyrosoopi'c tog applied as a level indicator.

igure 2 is a detail view of the pivot. As shown in this drawing, thebody a of the top has a pivot b the end of which has the form of asphere or of a portion of a sphere 0, also the whole of the body dandcentre of this sphere or portion of a spherec of the pivot.

zontal accelerations and to other lateral forces, as far as these havepreviously determined a movementof'the top parallelto itself, suflicientto move the point of contact of the pivot sphere .upon the bearing. Inpractice these actions, if they are of feeble duration relatively to theconditions of utlization, will not disturb the position of equilibriumof the gyroscope, in contradistinction tothe ease in which (as'in therection.

present gyroscopictops) they act directly upon the mass of agyroscopesuspended pendularly, that is to say the centre of gravity ofwhich is situated below the point of the pivot.

Experience shows that the axis of a top constituted according to thepresent inven tion, rotating at a low speed (500 to (300 revolutionsonly), forms an instantaneous and stable indicator of the vertical, thecorrection of which in case of disturbance is direct, without precessionor oscillation and the disturbances of which under the action ofmomentary lateral forces are particularly feeble. This result, which hasnot hitherto been obtained by any system of gyroscopic top, renders thepresent top particularly suitable for the realization of an inclinationindicator for aerial or maritime navigation.

The body a of the top may present as shown in Figure 1 an externalsurface a of spherical form concentric with the pivot sphere c. I

In this case, the properties of the pivot sphere being extended to thesurface of the body of the top, the latter reacts, under the action of atangential contact effected above its equatorialplane, by a correctionin a determined direction, that is a positive correction; on thecontrary, if the contact is effected below this lane, by a correction inthe opposite direction, that is a negative cor- By the term equatorialplane is meant a plane perpendicular to the axis of rotation of'the topand passing through the center of gravity of the top. Consequently, whenthe body of the top has a spherical ex ternal surface, the axis of thetop will be moved in a pre-determined direction if a contact is appliedto said spherical surface at a point located above the equatorial plane;

if the contact is applied at a point below said plane the axis of thetop will be moved in the reverse direction; finally. if the contact isapplied at the point on the circle located within said equatorial plane,the axis of the top will not be displaced.

The equatorial plane constitutes therefore a neutral plane in whichtangential forces may be exerted upon the body of the top without theequilibrium of the latter being disturbed.

The present system of g vroscopic top by reason of its special qualitiesis capable of receiving numerous industrial applications; this top maybe utilized in particular for the constitution of horizon indicatingapparatus in this case, the apparatus will be provided with anyappropriate arrangement capable of measuring relative inclinations ofthe axis or of the equatorial plane of the top with relation to themounting of the instrument, such as a mirror, a luminous spot, an index,carried by the axis of the top, etc.

This system of gyroscopic top is likewise applicable, by reason of theabove faculty of supporting equatorial contacts without disturbance, tothe realization of an arrangement for operating a servo-motortransmitting to a distance the variations of position of the top, eitherto indicating apparatus distributed at different points, where it isnecessary to let the measure of the inclination be known, or toautomatic operating apparatus, such as diving orsteering rudders,intended to ensure automatically the keeping of an airship or submarinein a determined position of equilibrium.

Fig. 5 shows diagramn'iatically, and by way of example, a device forfollowing up the lateral tilts of'the improved gyroscopic top. The topIt carries in its equatorial plane two fiexible'brushes m mdiametrically opposed to one'another; these brushes engage the smoothinner surface of a spherical housing within which is mounted the support(I of the top. The said housing comprisesfour spherical segments 1;, 0,p, g of metal, separated from one another by insulating rings 7", s,situated in two perpendicular planes, one of said rings passing throughthe equatorial plane of the top when the latter is in its position ofequilibrium, the two left hand side spherical segments 91, 0, aretherefore diametrically opposed to the right hand side sphericalsegments p, g.

The lower left hand side segment at and the upper right hand sidesegment p are inserted in an electric circuit in which are comprised asource of electric power 6 and a small electric motor u. Likewise theupper left hand side segment 0 and thelower right hand side segment areinserted in a circuit which isindependent of that above.

referred to, and in which are also comprised masses a source of electricpower '0 and a small motor w.

The spherical housing within which the top rotates is carried by twotrunnions and is movable about an axis perpendicular to the plane of thefigure and passing through the center of gravity G of the top. Thisspherical housing is susceptible of being moved in one or the otherdirection by the action of the motors u, 10 when the circuit of one ofthese is closed, as explained below; to this effect each motor transmitsits movement to the spherical housing with a reduced speed, as forexample, through a train of reducing gears in mesh with an outer toothedring a: on the spherical hous- Ihe operation of the device is asfollows:

In the position of equilibrium, the brushes m m engage theinsulatinghorizontal crown 9"; the two electric circuits are interrupted, themotors u w are not excited and therefore do not transmit any movement tothe spherical housing.

. As soon as the top tilts on its support, for example, in the directionof the arrow A, the two brushes m m engage the two diametrically opposedspherical segments, 0 g, and thus close the circuit of the motor w; thismotor, being excited, imparts to the spherical housing an angularmovement about its axis of rotation in the direction of 7 the arrowB,.-that is, in the opposite direction to the tilt of the top, until theinsulating ring 7' is brought back to the plane in which the brushes m mare moved. At this moment, the circuit of motor w is cut, the lattercomes to rest and the spherical housing stops. 4 i

f the top tilts in the opposite direction, the two brushes m m engagethe other two spherical segments p, n, and close the circuit of themotor u; this motor on becoming excited imparts to the spherical housingan angular movement in the direction of arrow C until the insulatingring is brought back to the plane of rotation ofthe brushes m m Thecircuit of the dynamo is then cut and the spherical housing stops.

The device just described enables the spherical housing to follow upallthe tilts of the top with the necessary motive power for actuatingany suitable mechanism.

I claim- 1. A gyroscopic top comprising a body, a

.spherical pivot the center of which coincides with the, center ofravity of the top, and

a spherical bearing or the pivot the radius the said bearing having aradius of curvature greater than that of the said spherical end portion.7

3. An apparatus for controlling a servomotor, comprising a bearing and agyroscopic top comprising .a body and a pivot, said pivot having aspherical end portion resting on said bearing, the center of saidspherical portion coinciding with the center of gravity of said top, thesaid bearing having a radius of curvature greater than that of the saidspherical end portion, and said body having an external surfaceconcentric with said spherical portion.

The foregoing specification of my improvements in or relating togyroscop'ic tops, signed by me this 18th day of Decemv ber, 1918.

EDWIE ETIENNE JOSEPH BONNEAU.

